Core B will produce recombinant gp120 in various forms for assay purposes and physical studies. Recombinant gp120 will be produced in a baculovirus/insect cell system which has been demonstrated to be successful. Core B will carry out assay procedures based on binding of gp120 to a version of CD4, both in cellfree and cell based assays. Finally, the core group will do experiments with live HIV in cell cultures to examine antiviral activities of test compounds generated at Procept, Inc.